Endoscopes are apparatuses that are widely used in the medical field and the industrial field. Particularly in the medical field, endoscopes are utilized in the diagnosis of observed sites by acquiring images inside body cavities. There are folds and ridges inside body cavities, often resulting in complex shapes.
A conceivable method is to increase the angular field of an objective lens of an endoscope, thereby widening the observation area laterally and rearward. Doing so facilitates observation of a large area inside a lumen. At this time, it is also necessary to expand an illumination area laterally simultaneously with the expansion of the angular field to illuminate a sufficient region of the observation area. Known methods of illuminating laterally include a method in which a light guide is bent (for example, see Patent Literature 1) and a method of deflecting illumination light with a reflection member (for example, see Patent Literatures 2, 3, and 4).